Abstract
Mode-division multiplexing technology holds great promise for addressing the ever-increasing demand for data transmission capacity. This paper proposes a compact adiabatic mode (de)multiplexer [(de)MUX] using a subwavelength grating (SWG) waveguide in the silicon-on-insulator platform, with optimization for the TE0-TE1 and TE0-TE2 mode (de)MUXs. By introducing an SWG waveguide, the coupling strength of waveguides can be enhanced, making it possible for the realization of more compact adiabatic mode (de)MUXs. The adiabatic evolution lengths for TE0-TE1 and TE0-TE2 mode (de)MUXs are only 10 µm and 17.5 µm, respectively. The numerical simulation shows that the operating bandwidth of the proposed device is beyond 200 nm. For the TE0-TE1 mode (de)MUX, the insertion loss and mode crosstalk of TE0-TE1 mode conversion within the whole wavelength range of 1450–1650 nm are less than 0.25 dB and −32.0dB, respectively. For the TE0-TE2 mode (de)MUX, the insertion loss and mode crosstalk of TE0-TE2 mode conversion within the entire bandwidth are less than 0.26 dB and −27.4dB, respectively. The TE0-TE1 and TE0-TE2 mode (de)MUXs can be cascaded to form a three-mode (de)MUX. For TE0-TE0, TE0-TE1, and TE0-TE2 processes within the entire bandwidth, the mode crosstalks are less than −33.5dB, −26.1dB, and −25.8dB, respectively. The device is scalable to the conversion of TE0 mode to higher-order mode.